Here’s a little blurb from the Wikipedia article on the piece:

The Piano Concerto in A minor, Op. 16, composed by Edvard Grieg in 1868, was the only concerto Grieg completed. It is one of his most popular works and is among the most popular of the genre.

Grieg’s concerto provides evidence of his interest in Norwegian folk music; the opening flourish is based on the motif of a falling minor second followed by a falling major third, which is typical of the folk music of Grieg’s native country. This specific motif occurs in other works by Grieg, including the String Quartet No. 1. In the last movement of the concerto, similarities to the halling (a Norwegian folk dance) and imitations of the Hardanger fiddle (the Norwegian folk fiddle) have been detected.